1. Field of the Invention
This discovery and invention concern improvements in the flushing of impeller-shaft seals within working centrifugal pumps whenever and wherever such flushing is required (normally when there is a mixture of liquids and abrasive solids being pumped). And more particularly (but not by way of limitation), to specific methods and apparatus for supplying flush fluid to seal housing-enclosures of centrifugal pumps in such a manner as to provide for a more thorough and a more complete and a more efficient flushing of impeller-shaft seals and seal housing-enclosures, and thus thereby greatly prolong seal life in centrifugal pumps.
2. Description of the Prior Art
Consider the usual centrifugal slurry pump assembly (FIG. 2): An impeller shaft 11 turns an impeller 22 within pump cavity 29 inside pump case 28. Pump case 28 is mounted on pump case mounting plate 23 which is attached to a base 21. Also on base 21 is bearing housing 25 through which runs impeller 11. Within seal housing-enclosure 26 are seal seat 13 and seal(s) 14. Seat 13 is attached to seal housing-enclosure 26. Seal(s) 14 are fixed to impeller 11, turn with impeller 11, and are held in place against seal seat 13 by spring 31.
Previous-to-this-invention known methods and apparatus for prolonging the life of centrifugal pump impeller-shaft seals 14 when pumping abrasive slurrys under high pressure proved unsatisfactory in my applications; the seal life when pumping sand and gravel was from less than a DAY to at the most a WEEK; (more sand pumped, the shorter the seal life). After my theoretical analysis indi resulted in non-complete flushing due to the manner of the introduction of the flushing fluid flow; I experimented extensively in the field over many years with many different seal types and seal flushing methods and apparatus. As a result of this extensive and intensive experimentation in the course of my continuing alluvial diamond mining operations in the Orinoco river basin jungle in southern Venezuela, I have (FIG. 1) radially improved the impeller-shaft seal(s) life on my sand-and-gravel centrifugal pumps. The seals are now changed only when the pump is dismantled to change the impeller due to wear on the impeller (two to three MONTHS), and even then the seals are not yet really worn, but are changed anyway as a matter of prudence and convenience.
Prior to my invention, known apparatus, method, and practice (FIG. 2) for flushing centrifugal pump impeller-shaft seals 14 was to simply place an inlet pipe 27 for the flush fluid somewhere near the middle on the seal(s) housing-enclosure 26. This inlet pipe 27 was then connected via a hose 24 to a clean source of flush fluid, normally the same type of fluids as that being pumped. This flush fluid was supplied at a higher pressure than that which the pump developed so as to force flush fluid into the seal(s) housing-enclosure 26 and then out into the pump cavity 29 between the pump case 28 and the rear of the impeller 22, thus flushing abrasives-laden fluid-borne debris away from the seal(s) 14.
In (prior to this invention) standard accepted theory, the higher pressure of the flush fluid was presumed to be sufficient to insure that no abrasive-laden fluids from the pump cavity 29 entered into the seal(s) housing-enclosure 26.
In practice it rarely, if ever, worked this way. Somehow abrasive-laden fluids from the pump cavity 29 did enter the seal(s) housing-enclosure 26 and rapidly wore out the seal(s) 14 and seal seat 13. As this occurred, there was increasing leakage from the seal(s) 14, until finally complete seal failure allowed air to enter the pump cavity 29, which caused the pump to lose its pressure and stop pumping. To remedy this, the extensive labor, expense, lost time, and inconvenience to completely dismantle the pump and change the seals had to be undergone. Obviously, the longer the seal life, the better.